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Currently, Mesa uses the lowering pass MOD_TO_FRACT to implement mod(x,y) as y * fract(x/y). This implementation has a down side though: it introduces precision errors due to the fract() operation. Even worse, since the result of fract() is multiplied by y, the larger y gets the larger the precision error we produce, so for large enough numbers the precision loss is significant. Some examples on i965: Operation Precision error ----------------------------------------------------- mod(-1.951171875, 1.9980468750) 0.0000000447 mod(121.57, 13.29) 0.0000023842 mod(3769.12, 321.99) 0.0000762939 mod(3769.12, 1321.99) 0.0001220703 mod(-987654.125, 123456.984375) 0.0160663128 mod( 987654.125, 123456.984375) 0.0312500000 This patch replaces the current lowering pass with a different one (MOD_TO_FLOOR) that follows the recommended implementation in the GLSL man pages: mod(x,y) = x - y * floor(x/y) This implementation eliminates the precision errors at the expense of an additional add instruction on some systems. On systems that can do negate with multiply-add in a single operation this new implementation would come at no additional cost. v2 (Ian Romanick) - Do not clone operands because when they are expressions we would be duplicating them and that can lead to suboptimal code. Fixes the following 16 dEQP tests: dEQP-GLES3.functional.shaders.builtin_functions.precision.mod.mediump_* dEQP-GLES3.functional.shaders.builtin_functions.precision.mod.highp_* Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
File: docs/README.WIN32 Last updated: 21 June 2013 Quick Start ----- ----- Windows drivers are build with SCons. Makefiles or Visual Studio projects are no longer shipped or supported. Run scons osmesa mesagdi to build classic mesa Windows GDI drivers; or scons libgl-gdi to build gallium based GDI driver. This will work both with MSVS or Mingw. Windows Drivers ------- ------- At this time, only the gallium GDI driver is known to work. Source code also exists in the tree for other drivers in src/mesa/drivers/windows, but the status of this code is unknown. Recipe ------ Building on windows requires several open-source packages. These are steps that work as of this writing. - install python 2.7 - install scons (latest) - install mingw, flex, and bison - install pywin32 from here: http://www.lfd.uci.edu/~gohlke/pythonlibs get pywin32-218.4.win-amd64-py2.7.exe - install git - download mesa from git see http://www.mesa3d.org/repository.html - run scons General ------- After building, you can copy the above DLL files to a place in your PATH such as $SystemRoot/SYSTEM32. If you don't like putting things in a system directory, place them in the same directory as the executable(s). Be careful about accidentially overwriting files of the same name in the SYSTEM32 directory. The DLL files are built so that the external entry points use the stdcall calling convention. Static LIB files are not built. The LIB files that are built with are the linker import files associated with the DLL files. The si-glu sources are used to build the GLU libs. This was done mainly to get the better tessellator code. If you have a Windows-related build problem or question, please post to the mesa-dev or mesa-users list.